FIG. 7 shows an example of a plate laminate type heat exchanger of related art. A plate laminate type heat exchanger 500 shown in FIG. 7 includes front and rear end plates 51 and 52 and a plurality of pairs of core plates 53 and 54 (cores 55) laminated therebetween, and peripheral flanges of each of the pairs of core plates 53 and 54 (a peripheral flange 53a and a peripheral flange 54a, for example) are bonded to each other in a brazing process, whereby high temperature fluid and low temperature fluid compartments are defined by alternately laminating in the space surrounded by the end plates 51, 52 and the core plates 53, 54, and each of the fluid compartments communicates with pairs of circulation pipes 56a, 56b and 57a, 57b provided on the front end plate 51 in such a way that the circulation pipes jut therefrom. An intermediate core plate 27 having fins 25 formed thereon is interposed between each pair of the core plates 53 and 54 (see Japanese Patent Laid-Open Nos. 2001-194086 and 2007-127390, for example).
Each of the core plates 53 and 54 has a substantially flat-plate shape. An outlet port for high temperature fluid 58b and an inlet port for low temperature fluid 59a are provided in each of the core plates 53 and 54 on one end side in the longitudinal direction thereof. On the other hand, an inlet port for high temperature fluid 58a and an outlet port for low temperature fluid 59b are provided in each of the core plates 53 and 54 on the other end side in the longitudinal direction thereof. The inlet port for high temperature fluid 58a and the outlet port for high temperature fluid 58b, as well as the inlet port for low temperature fluid 59a and the outlet port for low temperature fluid 59b of each of the core plates 53 and 54 are disposed in the vicinity of the respective corners thereof, and the pair of the inlet port for high temperature fluid 58a and the outlet port for high temperature fluid 58b and the pair of the inlet port for low temperature fluid 59a and the outlet port for low temperature fluid 59b of each of the core plates 53 and 54 are located substantially on the respective diagonal lines thereof. Each of the pairs of core plates 53 and 54 form a core 55. A high temperature fluid compartment through which the high temperature fluid (oil or EGR gas, for example) flows is defined in each of the cores 55. On the other hand, a low temperature fluid compartment through which the low temperature fluid (cooling water, for example) flows is defined between cores 55. The high temperature fluid compartments and the low temperature fluid compartments communicate with the circulation pipes 56a, 56b and the circulation pipes 57a, 57b, respectively. The high temperature fluid and the low temperature fluid are introduced into the respective fluid compartments or discharged out of the respective fluid compartments via the circulation pipes 56a, 56b and the circulation pipes 57a, 57b. The high temperature fluid and the low temperature fluid, when flowing through the respective fluid compartments, exchange heat via the core plates 53 and 54. FIG. 8 shows the heat exchange process. The core plate shown in FIG. 8 differs from the core plate shown in FIG. 7 in terms of shape. In FIG. 8, the portions that are the same as or similar to those in FIG. 7 have the same reference characters.